(94) 



British specimens. It is said to grow in similar localities to those of 

 C. rubrum, which it very closely resembles, differing chiefly in its rather 

 smaller size, and in the colovured cellules extending through only a part 

 of the articulation, leaving a narrow pellucid band in the middle of 

 each, about one-fourth or one-fifth of its length. 



From all the other naked species of the genus, it may be readily 

 known by its robust stems, except from C. diaphanum, and from that 

 species it may be readily distinguished by the coloured cellules occupying 

 the greater portion of the articulation, whereas in G. diaphanum they are 

 confined to the dissepiment. 



The Hormoceras demrrens of Kiitzing's Phyc. Gen. seems to be a much 

 smaller plant, but in other resj)ects agrees very well with Torquay 

 specimens (see Phyc. Brit). 



We have frequently gathered, and often received from correspondents 

 a variety or rather a state of G. ruhricm as G. decurreyis. To us this 

 appears to be merely the ordinary form of G. 7'zibrnm in a state of 

 incipient decay ; the middle cellules of the articulation first losing 

 their colouring matter, become transparent, while those at the dissepi- 

 ment having it more condensed and more permanent, remain coloured, 

 leaving a pellucid band in the middle of the articulation, in which, 

 however, the empty cellules may by a careful inspection be readily 

 observed. 



CERAMIOM DECURRENS. 



EXPLANATION OF DISSECTIONS. 



Fig. 1. — Apex of a branch. 



2. — Longitudinal section from the middle of a branch. 



3. — Articulations from same place. — Phyc. Brit. All magnified. 



